I would definitely start by listening to some STR podcasts, follow some STR coaches that are more adding value then selling their program on social media, and do a deep dive into the STR community. But here are some answers to your questions....
1. Yes, you need a contract that way you and the owner have an agreement in writing, and everyone knows what is expected from each other. Ours is pretty close to a LTR contract but of course changed to fit the STR modal.
2. We get paid on the 15th of each month and we would send an invoice. Ideally it would be great if you could get a credit card on file and charge it every month. Of course, you should still send an invoice breaking down the gross income from the property, charges for your services, purchasing supplies, cleaner fees, etc.
3. If you're thinking of charging 20% then you would get that percentage out of each booking....after the stay has been completed and the OTA has paid out the money. So, if there's a discount or a cancellation, there's no haggle about who gets what, everyone gets paid after the stay has been complete. You would need to decide if your 20% comes out of the total before the OTA fees or after, and that should be in writing.
4. The guest actually pays the cleaning fee on a STR, but the OTA lumps it in the payout to the host. So, you would take that amount of money and pay the cleaner. Since you would be managing the property, it should be something you take care of.
5. Your idea of lawn and snow is exactly how we handle those services. The owner lines up who they want to do it....and yes if you have contacts suggest them!....and the owner would also work out payment with those companies. But you would be the main contact person, that way you know who is coming when and can warn guests and of course you would need to call the snow removal company when it's needed.
6. This question is entirely up to you! I'm sorry it was somehow missed on here that you're a realtor and there are strong opinions about management qualifications of STRs on this forum. But you can choose to have the listing in your name or use the owners name and add yourself as the co-host. If it's in your name you would "own" the listing, and vice versa if it's in the owner's name. So, if you think there might be a chance that later you would step away from this project, you could have it in the owner's name so they can keep the listing and reviews.
There are quite a few software's and tools you can use to make this an easy and seamless process. It can be a bit over whelming at times and interesting situations may arise, but if it's something you would like to try go for it! Start learning all you can and take the plunge, you never know what you might be good at and enjoy until you actually try it! If you have any more questions or would like to talk, feel free to reach out!